Piston pump



FIG. 1 is a front view of a first embodiment;

FIG. 2 is a rear view of the first embodiment;

FIG. 3 is a view from the lower end of FIG. 1;

FIG. 4 is a view from the upper end of FIG. 1;

FIG. 5 is a view from the right end of FIG. 1;

FIG. 6 is a view from the left end of FIG. 1; and,

FIG. 7 is a perspective view of the embodiment.

The broken lines are included for the purpose of illustrating elements of the piston pump that form no part of the claimed design. 

The ornamental design for “piston pump,” as shown and described. 